SB4 - Natural selection and Genetic modification Flashcards
Who developed the theory of specification?
Alfred Russel Wallace
Who is Charles Darwin?
- Scientist and naturalist
- Put forward the theory of evolution
–> Supported by experimentation + his knowledge of
geology and fossils that he discovered on a round the world expedition - Published ‘On the Origin of Species’
When did Charles Darwin publish ‘On the Origin of Species’?
1859
Why does variation exist within species?
As a result of mutations in DNA
What is survival of the fittest?
Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully
What is the process of speciation?
- Alleles which provide a survival advantage are selected for through natural selection.
- Populations of a species can become isolated
- Different alleles may be advantageous in the new environment, leading to them being selected for
- Over time the selection of different alleles will increase the genetic variation between the two populations
- When they are no longer able to breed together to produce fertile offspring, a new species has formed
Why was there a lot of controversy surrounding the theory of evolution?
- It contradicted the idea that God was the creator of all species on Earth
- There was not enough evidence at the time as few studies had been done on how organisms change over time
- The mechanism of inheritance and variation were not known at the time
When are bacteria labelled as resistant?
When they are not killed by antibiotics which previously were used as cures against them
How are new strains of a bacteria created?
Mutations during reproduction can result in new genes, such as the gene for antibiotic resistance
How does the presence of new, resistant bacteria supportive of Darwin’s theory of evolution?
Those with antibiotic resistance can reproduce and pass on the
advantageous gene to their offspring
Give an example of a bacteria which is resistant to antibiotics
MRSA
What is MRSA also known as?
Superbug
Where is MRSA common?
Common in hospitals: spreads when doctors and nurses move to different patients
What does fossil evidence show?
How developments in organisms arose slowly
What techniques can we use to date fossils?
Carbon dating
Name some human ancestors
- Ardi
- Lucy
- Homo Habilis
- Homo Erectus
Name the human ancestors in the order of the oldest to the youngest
- Ardi
- Lucy
- Homo habilis
- Homo Erectus
How long ago has Ardi lived?
4.4 million years ago
Describe Ardi’s structure
Contains many ‘humanoid’ features but also resembles an ape:
* May have been able to walk upright
* Very long arms
* Very long toes that stuck out on the side
How long ago has Lucy lived?
3.2 million years ago
Describe Lucy’s structure
- Could walk upright
- Small, chimp like skull and brain
How long ago has Homo Habilis lived?
2.4 - 1.4 million years ago
Describe Homo Habilis’ structure
- Short
- Long arms
- Walked upright
How long ago has Homo Erectus lived?
1.8 - 0.5 million years ago
Describe Homo Erectus’ structure
- Tall
- Strongly built
What does the discovery of Homo Erectus prove?
That humans originated from Africa
What are the names of the scientists that discovered homo erectus / habilis?
Louis and Mary Leakey
What can we use as part of evidence for human evolution?
Stone tools
What do stone tools show about us?
Stone tools have become more complex as our brains evolved in complexity
Describe the types of stone tools that Homo Habilis used
Used basic pebble tools created by smashing rocks together
—> Tools had simple uses
Describe the types of stone tools that Homo neanderthalensis & Sapiens used
Used pointed arrowheads, spears and hooks
—> Enabled more advanced tasks to be carried out, such as catching fish
What methods do we use to date stone tools?
- Radiometric carbon dating
- Stratifying rock layers
Explain what Radiometric carbon dating is
We do this by looking at the natural radioactive decay of an isotope of Carbon (Carbon-14) we can estimate how long ago an organism lived
Explain what Stratifying rock layers is
We do this by looking at the layer of sediment in which a rock. Each layer of sediment, and everything within it, must have been formed at the same time
—> Therefore, we can date once-living fossils in this layer
What is a pentadactyl limb?
A limb with five digits
What is genetic variation?
The characteristics of individuals vary due to differences in genes
Name the ways we can classify organisms
- Three Domains system
- 5 Kingdoms system
What are the groups in the 5 Kingdoms system?
- Animals
- Plants
- Fungi
- Prokaryotes
- Protists
What is each kingdom then subdivided into?
A phylum, class, genus, order and species
What is the binomial naming system based on?
Genus and species
What are the groups in the three domain system?
- Archaea
- Bacteria
- Eukaryota
What is Archaea?
Primitive bacteria which live in extreme environments such as hot springs
What is Bacteria?
True bacteria (despite having similar features to archaea)
What is Eukaryota?
Organisms who have a nucleus enclosed in membranes, includes the kingdoms protists, fungi, plants and animals
Explain how genetic analysis has led to the suggestion of the three domains system rather than the five kingdoms classification method
Developments in science such as the improvement of the microscope and increased knowledge of biochemistry found that some species were more distantly related than first thought
What is selective breeding?
When humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic
Describe the process of selective breeding
1) Parents with desired characteristics are chosen
2) They are bred together
3) From the offspring those with desired characteristics are bred together
4) The process is repeated many times until all the offspring have the desired characteristic
What are the problems with selective breeding?
- Can lead to inbreeding
- Offspring can have a greater chance of genetic defects being present
- Lack of genetic variation
- Ethical issues associated with selective breeding
What are the issues with inbreeding in selective breeding?
If the environment changes or there is a new disease , the species could become extinct as they all have the same genetic make-up
How does selective breeding cause ethical concerns?
Many people consider it unethical to selectively breed for characteristics wanted by humans if it means that the offspring will suffer, or have a reduced quality of life as a result
How does selective breeding lead to inbred species?
Breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals
—> Results in the reduction of the gene pool , as the number of different alleles reduce (as they mostly have the same alleles)
What are the benefits of selective breeding?
- Greatly increase the yield of a particular crop by selectively breeding only individuals that produce higher quality or a larger mass of food
- Individual plants or animals can be bred to be resistant to a particular disease
What is tissue culture?
A method of culturing living tissue
What are some uses of tissue culture?
- Can culture animal and human tissues outside of the body
- Can produce an entire field of identical cloned crops using just a small cutting
How would you preform a tissue culture on plants?
- Take the plant that you would like to clone
- Using tweezers, remove a piece of tissue from a fast-growing region of the plant, e.g the root or shoot tip .
- Using aseptic technique, place the tissue on a special growth medium (containing hormones and nutrients).
- Once the tissue has developed enough (e.g produced shoots and roots), it can be transferred to compost for further growth .
What are the benefits of tissue culture?
- Produces lots of offspring w/ desirable features
- Increasing the number of crops resistant to bad weather
- Can help extremely endangered species, or even bring back species that have become extinct
What are the risks of tissue culture?
- It may lead to human cloning
- Clones have a low survival rate, and tend to have some genetic problems
- Gene pool is reduced through producing clones - low diversity of population
What is genetic engineering?
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
What are the stages of genetic engineering?
1) Genes from chromosomes are ‘cut out’ using restriction enzymes
2) The same restriction enzymes are used to cut the vector (such as a virus or bacterial plasmid) into which the genes will be placed
3) Ligase enzyme is used to attach the sticky ends of the gene and the vector together, to produce a recombinant gene product.
4) The vector is placed in another organism at an early stage in development so the desired gene moves into its cells and cause the organism to grow with the desired characteristics.
Where is the vector placed in plants during genetic engineering?
Into meristematic cells which can then produce identical copies of the modified plant
What are genetically modified crops engineered to do?
To be resistant to insects and to herbicides
—> Results in increased yields as less crops will die
What is genetic modification in medicine used for?
Gene therapy
What is gene therapy?
Involves transferring normal genes (not faulty) into patients so the correct proteins are produced
What are the benefits of genetic engineering?
- Can mass produce certain hormones in microorganisms
- Can improve yields in agriculture
- Crops w/ extra vitamins can be produced in areas where they are difficult to obtain
How does genetic engineering improve yields?
- Improving growth rates
- Introducing modifications that allow the crops to grow in different conditions
- Introducing modifications that allow plants to make their own pesticide or herbicide
What are the risks of genetic engineering?
- Might have an effect on wild flowers & therefore insects
- People are worried that we do not completely understand the effects of GM crops on human health
- Pose a selection pressure
How does genetic engineering posing a selection pressure a risk?
Could lead to increased resistance in other species, creating super weeds and pests
How might genetic engineering have an effect on wild flowers & insects?
- GM crops are infertile and these genes could spread into wild plants, leading to infertility in other species
—> This affects the entire environment - Growing with herbicides and pesticides can kill insects and other plants, which would reduce biodiversity.
What is Bacillus thuringiensis?
The name of a bacteria that produces toxins that kill insect larvae
Why does having BT a useful function for crops?
Increases their insect resistance
How do we create BT crops?
Genes are cut out from the bacteria using restriction enzymes , and re-inserted into the crop using ligase
What are some benefits of BT crops?
Less of the crop gets eaten by insects, increasing the crop yield and profits
What are some risks of BT crops?
We don’t know if the toxin has any effect on human health
What methods can we use to cope with the demands of a growing human population?
- Fertilisers
- Biological control
How do fertilisers help to cope with the demands of a growing human population?
Fertilisers provide useful nutrients to plants, making them more resistant to environmental conditions and able to grow faster and larger —> Resulting in increased crop yields
How do Biological control help to cope with the demands of a growing human population?
Another species can be used to maintain / control another species but it does reduce biodiversity and has a knock-on effect across the whole ecosystem
What is Biological control?
The use of certain species to control population of other species
